1. Division of Infectious Animal Disease Research, National Institute of Animal Health, National Agriculture and Food Research Organization, Ibaraki, Japan
2. Oita Prefectural Oita Livestock Hygiene Service Center, Oita, Japan
3. The United Graduate School of Veterinary Sciences, Gifu University, Gifu, Japan
4. Joint Graduate School of Veterinary Sciences, Gifu University, Gifu, Japan